1. Field of Disclosure
The present disclosure of invention relates to a method of processing data and a display apparatus for performing the method. More particularly, the present disclosure relates to a method of processing image data signals for thereby improving expression of a sharp edged glyph such as an alphabetic character and a display apparatus for performing the method.
2. Description of Related Technology
Generally, a flat panel display apparatus may include a matrix of light outputting picture element units (pixel or subpixel units) such as the liquid crystal shuttered units of a liquid crystal display (LCD) panel. The LCD panel is caused to display a desired image using a selective light transmittance characteristic of its liquid crystal material and color filters as well as using a backlight providing assembly disposed underneath to provide light for controlled passage through the LCD panel. A conventional LCD panel has a striped RGB structure. The striped RGB structure includes red, green and blue subpixels, and each of the red, green and blue subpixels is arranged to form a continuous stripe of the subpixel's color in either the column that the respective R, G, B subpixel resides in or in the row of the subpixel's residence. The conventional RGB triad has a capability of providing its own full gamut spectrum of colors as well as a capability of providing a white light when the metameric triad of RGB primary colors are lit up according to an appropriate drive mix (e.g., all turned on to maximum drive).
Recently, so-called Pentile™ RGBW structures have been developed that feature a screen-populating, repeating group having red, green, blue and white subpixels. See for example U.S. 2008/0030526 (Brown Elliott et al.: Methods and Systems for Sub-Pixel Rendering with Adaptive Filtering) which disclosure is incorporated herein by reference. The Pentile™ RGBW structure may be advantageously used to decrease the number of subpixels actually present in the display area of the flat panel while providing an apparent resolution equal to or greater than that of a striped RGB structure having many more subpixels. Since the RGBW repeating group of the Pentile™ structure includes one or more white subpixels and these do not use a light-reducing color filter, an LCD panel having such an RGBW structure tends to have higher light transmittance efficiency when displaying unsaturated colors or black and white images so that luminance of the backlight assembly may be accordingly decreased to thereby reduce power consumption of the display apparatus. For example, for a display apparatus that is used in an office environment where black on white background typing is desired, black characters may be displayed on a white board background where the white board background is produced at least partly by the white subpixels, so that power consumption may be remarkably reduced relative to a display using only the striped RGB structure (and having corresponding R, G and B; light suppressing color filters). However, due to the discrete nature in which the RGBW subpixels are spatially arranged, the display apparatus having the RGBW structure may not display the character (or another glyph having slanted sharp edges, etc.) as an image that is perceived to be a smoothly formed one.
FIGS. 1A and 1B are respective conceptual diagrams showing how an alphabetic character “A” might be respectively displayed as a black filled glyph on a first display panel having the conventional striped RGB structure and on a second display panel having an RGBW structure (in this case an 8-cell RGBW repeating group).
Referring to FIGS. 1A and 1B, while the attempted display of the character “A” on the first display panel (RGB structured) is smoothly displayed, the attempted display of the same character “A” on the second display panel (RGBW structured) can appear distorted when the white board generating algorithm tries to make maximal use of the white subpixels and color balancing and the character “A” is therefore not always smoothly displayed on the display panel having the RGBW structure. More specifically, and comparing it to the idealized “A” shown in FIG. 1A, the RGBW formed “A” of FIG. 1B suffers from drawbacks such as that, some regions of the “A” character which should not be displayed as black are displayed as black, and some regions of the “A” character which should be displayed as black instead displayed as white. Yet more specifically, consider the interior white area of the capitol “A” glyph immediately below the apex of the “A”. In FIG. 1A this interior white area is displayed as two RGB triads lit up in a column and surrounded by black. However, in FIG. 1B this interior white area consists of one horizontal RGB triad in one row and just one lit-up W subpixel in the row below. Color balancing for providing a fully white color is thus preserved. However the shape of the intended “A” glyph is not preserved. Accordingly, the characters are not always smoothly displayed as originally intended on the display panel having the RGBW structures.